Custom (very) Quark esc heatsink...

[Patrick]

I don't know the specific max temp for the feigao's, but I think I've read most motors shouldn't go above 200f (93c) at max. I don't think I'd want mine any where near that hot though.
An unloaded 7xl on 16.5 v (since there'd be almost no volt drop unloaded) is going to be spinning near 40000rpm..not something I'd be doing to my motor for more than .5 of a second, if that.
It was never going to be a test for the ESC since it was at or near full throttle, and 140 watts at that voltage is less than 9 amps. So I'd be supprised if you felt heat in the ESC with no heatsink.